Osteoarthritis & Viscosupplementation

By Robert Flannery, MD
Lemak Sports Medicine
Primary Care Sports Medicine

I've been asked multiple times by multiple patients if I do, "those chicken injections?" I tell them yes, but we've come a long way from those first injections. The debate over viscosupplementation or Hyaluronic Acid (HA) injections has taken some interesting turns over the last several months.

Hyaluronic Acid is one of the many treatments for osteoarthritis (OA). The exact cause of osteoarthritis is still being researched, but we know the end result is loss of cartilage, "thinner" joint fluid, and the dreaded "bone on bone" X-ray report. There is no way to reverse the process and any "treatments" are only temporary. Most are used as a bridge to a knee replacement. However, for some people, that bridge is all they've got and we'll talk more about that later. Other treatments for OA include lifestyle modifications (rest, avoidance of the irritating activity, etc.), exercise, physical therapy, bracing, medications (NSAIDs, narcotics, etc.), weight loss, and corticosteroid injections. You'll notice that lifestyle modifications and exercise seem to be mutually exclusive. They are not, but it highlights the spectrum of treatments for OA and that there is not a good consensus on treatment.

Here is a little background on HA. Some of the first commercially available products were derived from rooster combs. Some products are still made from an avian source and some are made synthetically from a bacterial culture. Regardless of how it is made, the theory behind HA is two- fold. First, it is to bath the joint in HA in hopes that receptors in the cartilage will "remember" what joint fluid should be and begin making more appropriate joint fluid. Second, it will provide some lubrication to the joint until the medication can take effect. The "gel" is injected directly into the joint (ultrasound guidance can be used, but that is a topic for another blog). This can be done in a single injection or up to 5 weekly injections. Results can be seen immediately, but may take a few weeks to take effect. Maximum benefit is usually seen by 6 weeks and typically lasts around 6 months. The decision as to which product to use and the number of injections is made on an individual basis by the physician and the patient.

Recently, there was a change in the 2013 recommendation guidelines for OA of the knee by the American Academy of Orthopedic Surgeons (AAOS) from inconclusive to strongly against HA injections. The full OA guidelines can be found here (http://www.aaos.org/research/guidelines/TreatmentofOsteoarthritisoftheKneeGuideline.pdf). The recommendation regarding HA is #9. I, along with many in my field of primary care sports medicine, am concerned with these changes. Why is this a concern? It all comes down to reimbursement or the lack there of. There is no denying that the cost of HA injections is high (again a topic for another entry). Insurance companies base their reimbursements on guidelines and recommendation of respected academies and societies, especially when considering an expensive treatment option. We are starting to hear and see some rebuttals to the AAOS. Most notably by the Arthroscopy Association of North America (AANA), American College of Rheumatology (ARC), and Osteoarthritis Research Society International (OARSI), which have returned "uncertain" guidelines. They have all been critical of the methodology used by the AAOS in its meta analysis. A recent article by Dr. Bannuru, a leading expert in meta analysis, pointed out numerous flaws in how AAOS “missed the mark” in developing the recommendations.

The short version of my concerns with this recommendation is as follows. The most glaring is that safety profile is not taken into account, especially when discussing HA vs NSAIDs or Tramadol. HA injections have a very minimal side effect profile and have been routinely found to be safe. NSAIDs, which are currently the gold standard for treatment, or Tramadol, have a well-known side effect profile including bleeding, GI, kidney, and cardiovascular risks. Cost also has to be taken in to consideration when making the argument in HA vs NSAIDS. If you look solely at administration cost, NSAIDs will win out. However, if using NSAIDs as a long term treatment, I believe the cost of complications both monetarily and in quality of living will favor HA. That being said, you can make the argument that NSAIDs should only be used as a bridge to knee replacement. My response would be, "what about the patients that cannot have surgery due to other comorbidities?" This is a patient population that usually already has issues with renal, GI, and cardiovascular disease. A lot of them cannot take NSAIDs, cannot exercise because their joints hurt, and corticosteroids have a worse side effect profile. HA injections can be very useful in this subset of patients. On the other end of the surgery spectrum are young patients with OA. We know that joint replacements will last approximately 15 to 20 years. Ask any orthopedic surgeon and they will tell you that replacing a joint replacement is no fun. If possible, I try to "bridge" patients until their early to mid 60s before having a joint replacement. I cringe at putting a 40 year old on NSAIDs for 20+ years. Yes, the younger patient will do better with weight loss, exercise, and PT, but they usually get better results from HA injections as well.

Second, there are multiple factors to interpret when looking at the effects of HA injections including type of medicine, age, overall health, progression of the disease, and metabolism of the HA. This fact makes it very difficult to make a single overarching statement regarding the utility of viscosupplementation. There are multiple types of HA injection, high, low, and mixed molecular weight preparations. The AAOS guidelines document identified that the efficacy of high molecular weight preparations were significantly better.  However, in the recommendation, AAOS did not differentiate among the products.  In fact, AAOS included some HA preparations that are not approved for use by the FDA. When looking at the remaining variable factors patient selection will cover age, health, progression of the disease, and metabolism of the medication. The AAOS guidelines do not mention patient selection. Three of the four are easily identifiable and obviously the younger, healthier, and less disease a person has, the better they will respond to any intervention. Metabolism is very difficult to predict. Some patients will be "responders" and some will be "non responders". Unfortunately, at this time the only way to identify this is trial and error, but research is being conducted.

In conclusion, I feel that the 2013 AAOS guidelines are flawed. At worst, an "inconclusive" or "uncertain" recommendation could have been made. At best, multiple recommendations for high vs. low molecular weight HA and proper patient selection could be made. Viscosupplementation is a viable treatment option. It has an outstanding safety profile and can be used in conjunction with other conservative measures. It can be used as either a bridge to knee replacement surgery or for long term treatment. Further research needs to be done to address efficacy and metabolism. In the meantime, we need to do what we can for our patients with OA and that should include the option for hyaluronic acid injections.